ER Goodenough was a Yale Professor of Religion and an expert on Hellenistic Judaism who had some involvement in another longstanding project of the Rockefellers, the $2mln Palestine Archaeological Museum (1930-1938).
This book was an extremely important influence on the conceptualization of the Alcoholics' bible. Goodenough's thesis is that an actual Jewish mystical cult (p.36 "mystery religion") was hidden behind the writings of Philo Judaeus.
In the USA, works published before 1964 are now
in the public domain if the copyright was not renewed 28 years later. E.R. Goodenough was still alive, but copyright was not renewed (in 1963, or thereafter). Renewed copyrights can be found at https://cocatalog.loc.gov/